How to search for files in classpath?

What is the best way to search for all files of a particular type, e.g. "*.mytestfile" in module classpath, including searching within dependency JARs?

I tried using FileTypeIndex but it did not return any result? Ideally I'd like to get a list of URLs, e.g. jar:file:/my/path/file.jar!/com/foo/bar/file1.mytestfile, etc.